COR2 CME - August 21, 2007

The COR2 coronagraph on STEREO (ahead) caught this coronal mass ejection (CME) as it blasted into space on August 21, 2007. A CME is a cloud of charged particles unleashed by the Sun when magnetic forces clash near the surface of the Sun. Because the Sun has been near its solar activity minimum for some time, such sights are pretty rare. In coronagraphs the Sun and some area beyond it are blocked out by an occulting disk so that we can see the faint structures in the corona. Here we added an image of the Sun taken in extreme ultraviolet light at about the same time so our viewers can get a sense of the scale involved.